An air heat exchanger includes two tubular headers through which a cooling medium flows, a plurality of flat tubes arranged to couple the two headers, and a plurality of heat transfer fins provided between the plurality of flat tubes. Each of the flat tubes is orthogonal to the header and each of the heat transfer fins is orthogonal to the flat tube. A plurality of minute flow channels communicating from the headers are formed in the flat tubes. The cooling medium flows from the header to the flat tube through the flow channel. Each of the header, the flat tube, and the heat transfer fin is formed of a metal material having high thermal conductivity, for example, aluminum. These members are bonded to each other by a brazing material or an adhesive material. Air is blown on the air heat exchanger having such a structure using a fan and the air is introduced into the air heat exchanger.
In the air heat exchanger, a heat exchange of the cooling medium and the air is performed. The cooling medium is introduced into the header and is then distributed to the flat tube through the flow channel. Hot heat or cold heat of the cooling medium introduced into the flat tube is transmitted from the flat tube to the heat transfer fin to expand a heat transfer area and performs a heat exchange with the air flowing between the heat transfer fins.
However, when the air heat exchanger is used as an evaporator, temperatures of surfaces of the flat tube and the heat transfer fin are lower than a temperature of the air. For this reason, when the air passes between the heat transfer fins, moisture in the air condenses into the surface of the heat transfer fin. In the air heat exchanger in which the flat tubes are arranged to extend in a gravity direction and the heat transfer fins are arranged horizontally, condensation water generated on the surfaces of the heat transfer fins is rarely moved by an action of gravity and the condensation water is hard to be drained. In addition, if the condensation advances and a large amount of condensation water stays between the heat transfer fins, the condensation water may occlude between the heat transfer fins. If between the heat transfer fins are occluded, ventilation resistance of the air heat exchanger increases, which results in deteriorating heat exchange efficiency of the cooling medium and the air. In addition, the condensation water is swept by ventilation air and is scattered on the downwind side of the heat transfer fins and water droplets are blown out from the air heat exchanger.
For this reason, a structure for efficiently draining the condensation water generated in the heat transfer fins in the air heat exchanger is studied. For example, PTL 1 discloses an air heat exchanger in which openings are provided in heat transfer fins to drain condensation water on surfaces of the heat transfer fins. In addition, PTL 2 discloses an air heat exchanger in which condensation water is dropped by inclining heat transfer fins.